Field of the Invention
The present utility model relates to the field of magnetic resonance imaging, in particular to a gradient coil checking device.
Description of the Prior Art
Magnetic resonance imaging (MRI) is a technology in which the phenomenon of magnetic resonance is utilized for the purpose of imaging. The principles of magnetic resonance are as follows. When an atomic nucleus contains a single proton, as is the case for the nuclei of the hydrogen atoms that are present throughout the human body, this proton exhibits spin motion and resembles a small magnet. The spin axes of these small magnets normally lack a definite pattern, but when an external magnetic field is applied, the small magnets will be rearranged according to the magnetic force lines of the external magnetic field. Specifically, they will align in two directions, either parallel or anti-parallel to the magnetic force lines of the external magnetic field. The direction parallel to the magnetic force lines of the external magnetic field is called the positive longitudinal axis, while the direction anti-parallel to the magnetic force lines of the external magnetic field is called the negative longitudinal axis. The atomic nuclei only have a longitudinal magnetization component, which has both a direction and a magnitude. A radio frequency (RF) pulse of a specific frequency is used to excite the atomic nuclei in the external magnetic field such that their spin axes deviate from the positive longitudinal axis or negative longitudinal axis, giving rise to resonance—this is the phenomenon of magnetic resonance. Once the spin axes of the excited atomic nuclei have deviated from the positive or negative longitudinal axis, the atomic nuclei have a transverse magnetization component.
When emission of the RF pulse has ended, the excited atomic nuclei emit an echo signal, gradually releasing the absorbed energy in the form of electromagnetic waves, such that their phase and energy both return to the pre-excitation state. An image can be reconstructed by subjecting the echo signal emitted by atomic nuclei to further processing. The echo signals are spatially encoded by gradient magnetic fields produced by gradient coils, so that the location from which the echo signals originate can be determined by further processing of the detected (received) echo signals, so that an image can be generated.
At present, MRI systems require stronger gradient magnetic fields during application than in the past, therefore ever greater currents must be applied to the MRI system gradient coils.
Under the action of such powerful currents (hundreds of amperes), damage to gradient coils may result if there are any connection defects during manufacture or integration of the gradient coils. An example of the most direct damage is destruction by burning.